Charts / Trends - Sleep as Android

Documentation
1

Charts enable you to study your sleep from a long-term perspective.

Charts are here to help you find patterns in your sleep and enable you to decide for evidence-based changes.

This is a companion discussion topic for the original entry at https://sleep.urbandroid.org/docs/sleep/charts.html
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I have a question about how statistics are calculated in the Advice section. Is it using the data of each individual sleep period separately in its calculations, or the data averaged (or summed, in the case with Sleep Duration) over the whole day?

For example, if I take a 30 minute nap, rate it 4 stars, have 0% deep sleep (since it is a nap), and 75% efficiency, does that end up as its own data point on the Advice charts, or will it be averaged with the rating/deep sleep/efficiency of the main sleep of the day before it is used to form the regression models?

And how does bedtime figure into this? How does the app determine my bedtime if I have biphasic sleep? Is it confused by multiple sleep periods in the same day?

Thanks